In the prior art, it is known to manufacture razor blades having various coatings which have been developed to provide the blades with a protection against abrasion and atmospheric conditions as well as contact with various materials during storage or the shaving process which materials would tend to degrade the basic material of the blade.
In addition to the protection of the material from which the blade is manufactured, the various coating supplied to the blade edges have been formulated with an attempt to eliminate the undesirable effects which occur in the shaving process that may cause irritation to the skin of the blade user. Materials exhibiting a low coefficient of friction are commonly used for this purpose.
In order to accomplish the above, blades have been treated by the coating of a polymeric material to the surface of the blade cutting edge by means of a melting process. Generally, the process of applying the polymer material to the razor blade is accomplished by spraying a polymeric material dispersed in solution to the blade and heating the blade in a non-oxidizing environment causing the polymeric material to melt and spread onto the blade edge surface. When the blade is ultimately cooled, the coating solidifies and remains adhered to the blade. Heating of the blade to produce this melting has, in general, been accomplished by infrared, inductive or resistance heating of the blade to a temperature in a range of between 200.degree. C. to 400.degree. C. Various examples of such a process are disclosed in U.S. Pat. No. 3,224,900 to Creamer et al and U.S. Statutory Invention Registration H640 to Nizel.
Resistance and inductive heating have high energy consumption and take long a time to heat the blades, since they heat the entire mass of blades including the blade carrier or fixtures. Although infrared heating is slightly faster than resistance or inductive heating--taking only 40 seconds to heat a foot long (12 inch ) stack of blades compared with about 20 to 30 minutes in resistance or inductive heating--the processing window is actually quite small due to the emissivity of the blade stacks which vary with the angle of sharpened blades. Furthermore, the cooling time required before the coating solidifies enough for the blades to be handled is still quite long.
It is an object of the present invention to provide an improvement to the prior art process of applying a coating of polymeric material to the edge surfaces of a razor blade through the introduction of radio frequency heating, preferably microwave heating, in the manufacturing process.
Another object of the invention is to reduce the heating and cooling times required to meld and solidify polymeric coating materials without adversely effecting the blade edge.
An additional object is to produce coated blades with good bonding of polymer to the substrate cutting edge.
Still a further object of the invention is to reduce the energy requirements for melting of the polymeric material to the blade edge surface by the use of microwave energy.